There is a need for improved high-energy optical pulse generation for a number of applications including LIDAR (light detection and ranging) and in particular LADAR (laser detection and ranging) for detecting objects (particularly flying objects) at great distances, as well as for imaging, medical treatments and materials processing.
Optical amplifying fibers can have very high gain. When pumping such fibers to very high energies, the high gain starts to amplify spontaneous emission (ASE), which depletes and wastes pump power, as well as generating undesired optical output.
Papers that describe fiber amplifiers include T. Komukai, T. Yamamoto, T. Sugawa, Y. Miyajima, “Upconversion Pumped Thulium-Doped Fluoride Fiber Amplifier and Laser Operating at 1.47 μm”, IEEE J. Quantum Electron, Vol. 31, no. 11, pp 1880-1889, 1995 (hereinafter “Komukai et al. 1995”); B. N. Samson, N. J. Traynor, D. T. Walton, A. J. G. Ellison. J. D. Minelly, “Thulium-doped silicate fiber amplifier at 1460-1520 nm”, Proc OAA, paper PD3, Quebec City, 10th, 2000 (and in Optical Amplifiers and Their Applications, OSA Technical Digest (Optical Society of America, Washington, D.C., 2000), pp. PD6-1) (hereinafter “Samson et al. 2000”); R. H. Stolen, E. P. Ippen, “Raman gain in glass optical waveguides”, Applied Physics Letters, Volume 22, Issue 6, pp. 276-278, 1973 (hereinafter “Stolen et al. 1973”); and J. E. Townsend, W. L. Barnes, S. G. Grubb, “Yb3+ sensitised Er3+ doped, silica-based optical fibre with ultra-high transfer efficiency”, Proceedings Materials Research Society (MRS) Symposium Proceedings Optical Waveguide Materials, Eds. M. J. Broer, G. H. Sigel Jr., R. T. Kersten & H. Kawazoe, Boston December 1991, 244 ISSN 0272-9172, pp. 143-146 (hereinafter “Townsend et al. 1973”); which are each incorporated herein by reference.
Improved apparatus and methods are needed to generate high-energy optical pulses.